Concepts of Forensic Science for Lawyers

Prof. Prashant Mehta

What is Forensic Science

• A special discipline (also called

criminalistics) that is used to

discover the facts about what

happened during a crime.

• It is the study and application of

science to matters of law (criminal

and civil) “science in the service of

law”.

• Includes providing timely, accurate,

and thorough information to all levels

of decision makers in our criminal

justice system.

• A criminalist examines physical evidence for legal purposes

• Criminologists study the crime scene for motive, traits, and

behavior as to help interpret the evidence.

– They learn to think like criminals

Criminalists vs Criminologists

What happens at a crime scene?

• The first responding officer must secure and protect the

integrity of the crime scene. This is a very important

task! Sometimes crimes cannot be solved and criminals

are set free because the crime scene was not properly

processed.

– Gather information– Search for evidence– Document evidence– Collect evidence– Preserve evidence so it remains

exactly as it is found at the scene– Conduct field tests– Reconstruct the sequence of events

The primary crime scene is the location where the crime was committed such as a homicide or a

robbery. A secondary crime scene could be the location where a murder victim was buried, the

victim’s home where evidence of the assailant is found, or a suspect’s home where fibers from the

victim’s clothing or hair were found. In order for a location to become a crime scene, there must be

evidence found at that site.

Primary vs. Secondary Crime Scenes:

• Locard's Exchange Principle states that with contact between two

items, there will always be an exchange. This is the basis of trace

evidence collection at a crime scene. “Every contact leaves a trace”

Chain of Custody

• The collection, labeling, and testing of evidence. There

must be a documented trail of exactly who has handled the

evidence from crime scene to court. If the chain of

custody is broken because of improper handling or

labeling of evidence, then the evidence may not be

admissible in court.

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Forensic Area

Collect evidence (non-bodily)

Interrogate witnesses

Arrest criminals

Investigate crime scene

CRIMINALISTICS (Forensic Laboratory Experts)

LAW ENFORCEMENT (Homicide detective, police, FBI, profilers, others)

MEDICAL EXAMINER

Forensic Chemist / Toxicologist

Questioned Document Examiner

Trace Evidence Specialist

Serologist / DNA Analyst

Firearms and Toolmarks Examiner

Latent Fingerprint Examiner

Forensic Pathologist

Forensic Entomologist

Deputy Medical Investigators

Forensic AnthropologistPhotos, sketches, notes

Bloodspatter Analyst

• Applies the principles and

techniques of the physical and

natural sciences to the analysis of

the many types of evidence that may

be recovered during a criminal

investigation

• May also provide expert court

testimony - Known as an expert

witness - Individual whom the court

determines possesses knowledge

relevant to the trial.

Forensic Scientists

Developments in Forensic Science

• 700s AD - Chinese used fingerprints to establish identity of

documents and clay sculptures

• ~1000 - Roman courts determined that bloody palm prints were used

to frame a man in his brother’s murder

• 1149 - King Richard of England introduced the idea of the coroner to

investigate questionable death

• 1200s - A murder in China is solved when flies were attracted to

invisible blood residue on a sword of a man in the community.

• 1776 - Paul Revere identified the body of General Joseph Warren

based on the false teeth he had made for him

Developments in Forensic Science

• 1784 - John Toms convicted of murder on basis of torn edge of wad of

paper in pistol matching a piece of paper in his pocket

• 1879 - Alphonse Bertillion developed a system to identify people using

particular body measurements

• 1896 - Edward Henry developed the first classification system for

fingerprint identification

• 1900 - Karl Landsteiner identified human blood groups

• 1904 - Edmond Locard formulated his famous principle, “Every

contact leaves a trace”

• 1984 - Jeffrey’s developed and used the first DNA tests to be applied

to a criminal case

People of Historical Significance

• Mathieu Orfila- father of forensic toxicology

• Alphonse Bertillion- devised first scientific system of personal

identification

• Francis Galton- conducted first definitive study of fingerprints and

their classification

• Leone Lattes- developed a procedure to determine blood type

from dried bloodstains

• Calvin Goddard- used a comparison microscope to determine if a

particular gun fired a bullet

People of Historical Significance

• Albert Osborn- developed the fundamental principles of

document examination

• Walter McCrone- utilized microscopy to examine evidence

• Hans Gross- wrote treatise on criminal investigation

• Edmond Locard- considered the father of criminalistics;

responsible for Locard’s exchange principle

– States that when a criminal comes in contact with an object

or a person, a cross transfer of evidence occurs

Disciplines in Forensics

• Anthropology – examine bones to identify remains and determine other

information such as age, race, and gender

• Art – identify missing children, victims, or suspects through

reconstructive techniques based on age progressions, composite

imagery and knowledge of human anatomy.

• Crime Scene Investigation – gathering information at a crime scene,

collect and preserve evidence

• Criminalistics – collect, identify, and analyze physical evidence from a

crime scene

Disciplines in Forensics

• Engineering – determine material or structural failures and reconstruct

events such as accidents or collapse of buildings

• Entomology – study insects found on a decomposing body to

determine time of death

• Jurisprudence – study philosophy of law.

• Medicine (Pathology) – study injuries and disease to determine cause

and manner of death through an autopsy

• Odontology – dentists that identify human remains by matching dental

records, and identify bite marks

Disciplines in Forensics

• Psychology & Psychiatry – study human or criminal psychology

and behavior, and profile criminals and victims

• Toxicology – identify and analyze poisons, drugs, and chemicals

and study their effects.

Forensic Techniques

DNA Analysis

Use molecular biology to

extract and analyze DNA

from blood, semen, bones,

body tissue, hair roots,

saliva, fecal matter, and any

other material

Forensic Techniques

Firearms Examination / Unit

Analyze firearms, discharged bullets, cartridge cases,

shotgun shells, unusual or homemade weapons, and

ammunition components. They determine what kind of

weapon fired a bullet, match bullets to specific weapons,

and determine the trajectory and distance of a shot.

Forensic Techniques

Forensic Drug Analysis

Analytical chemistry is used to

identify the presence and quantity

of controlled substances. A drug

chemist analyzes unknown

powders, liquids, plants, pill,

capsules, and other forms of drug

Forensic Serology - Identify blood and other body fluids

Impression evidence

Study various types of markings on evidence, such as footwear

impressions, tire impressions, and footprints

Latent Fingerprints

latent fingerprints are invisible to the human eye. Fingerprints are

detected, developed, and processed in order to compare them to

known fingerprints for identification

Questioned Document Examination

scientific examination of handwriting, typewriting, printing, photocopying, or other

mechanical production of written material. Identify ink, paper, or other document

components for authenticity, forgery, or alteration

Trace Evidence

examine hair, fibers, glass, soil, plants, minerals, and many other

different types of materials. Substances are studied under a

microscope and chemical techniques can be used to identify and

individualize evidence even when found in very small quantities

Voice Analysis

ties unknown voices in recorded messages to particular speakers

based on speech patterns that are unique to every individual

Photographic Unit

• Applies specialized photographic techniques for recording and

examining physical evidence

All About Evidence

• Is any item or information gathered at the

scene of a crime, or at related locations

which tends to disapprove or establish

something.

• Any tangible material that can be used to

prove the facts of a matter in a court of law.

• Expert witness: someone who testifies in

court as a qualified expert in a particular

subject area

It can be divided into two general goods:

• Testimonial Evidence

• Physical Evidence

Evidence

Physical Evidence

• Tangible tend to prove or disapprove a fact• Real evidence• Refers to any item that would be present at the crime

scene on the victims out found in a suspects possession.• more reliable than testimonial evidence• Can be any material or object in any shape, size, form.

Physical Evidence

• Types of Physical Evidence:• Trace Evidence• Transient Evidence• Conditional Evidence• Indirect Evidence• Individual Evidence• Class Evidence

Trace Evidence

refers to physical evidence that is found in small but measurable amounts. (For example: hair, fibers, skin cells, DNA, blood, etc.)

Transient Evidence

temporary evidence can be easily changed or lost. Recorded at the time by usually the first office at the scene. (For example: odors, temperature, imprints, etc)

Conditional Evidence

produced by a specific action or event at the scene. (For example: lights, doors, windows, position of furniture, etc)

Indirect Evidence

does not prove or disprove a fact in question. (For example driving under the influence)

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Individual Evidence

can be related to a single source. (For example fingerprints. Handwritings, etc)

Class Evidence

Can be associated with a group of items that share properties or characteristics. (For example: blue jeans)

Arson Evidence

Physical Evidence

Chemistry

The study of composition, structure, properties, and reactions of a substance which help us identify a suspect. Identify and analyze toxic substances, fire accelerants, gunpowder residue, explosives and other chemical substances.

Biology

The study of the investigation of living matter, or once living matter, in reference to its origin, behaviour, and classification. Applies the knowledge of biological sciences in order to investigate blood samples, body fluids, hair, and fiber samples.

Physics

The study that comprises of all investigations that deal with motion, force, and dynamics. Incorporates the principles of chemistry, physics, and geology to identify and compare physical

evidence.

Other Crime Lab Services

• Toxicology Unit- examines body fluids and organs for the

presence of drugs and poisons

• Latent Fingerprint Unit- processes and examines evidence for

latent fingerprints

• Polygraph Unit- conducts polygraph or lie detector tests

• Voiceprint Analysis Unit- attempts to tie a recorded voice to a

particular suspect

• Evidence Collection Unit- dispatches specially trained personnel

to the crime scene to collect and preserve physical evidence

Other Forensic Science Services

• Forensic Pathology- concentrate closely on the understanding of

types and causation of injuries and causes of sudden and

unnatural death

– Deals with the different stages of death

• Rigor mortis- stiffening of the body (occurs within first 24 hours)

• Livor mortis- settling of blood closest to the ground (occurs up to 12

hours)

• Algor mortis- results in loss of heat

Other Forensic Science Services

• Forensic Anthropology-concentrates on the identification of

deceased individuals whose remains are decomposed, burned,

mutilated or otherwise unrecognizable

• Forensic Entomology- is the study of insects and their relation to

a criminal investigation, commonly used to establish the time of

death

• Forensic Psychiatry- work with courts in evaluating an individual's

competency to stand trial, defenses based on mental diseases or

defects (e.g., the "insanity" defense), and sentencing

recommendations

Other Forensic Science Services

• Forensic Odontology- evaluates teeth to determine the identification of the deceased

• Forensic Engineering- investigation of materials, products, structures or components that fail or do not operate/function as intended, causing personal injury for example

• Cyber technology- involves the examination of digital evidence

ListeningAttentionPatience

Questions